1. Field of the Invention
This invention relates to electroless metal plating of aramid surfaces wherein the metal is strongly adhered to the aramid substrate and provides a highly conductive surface. The aramid includes a small amount of polyvinyl pyrrolidone as an additive polymer which improves the plating quality, the adhesion, and, consequently, the conductivity of the metal coating.
2. Description of the Prior Art
Electroless plating is the deposition of a metal film by interaction of a metal salt and a chemical reducing agent. Electroless plating, in a general way, is well known. One of the difficulties in achieving successful electroless plating has resided in obtaining good adhesion between the plating substrate and the plated metal. While mere encapsulation may suffice for some applications and some articles, good adhesion of the plated metal is essential for fibers because the plated metal coating must withstand the forces of further processing.
U.S. Pat. No. 4,614,684 issued Sep. 30, 1986 on the application of Ebneth et al. discloses that a fabric of poly(p-phenylene terephthalamide) (PPD-T) fibers can be nickel plated by a rather complicated process which includes activating the fabric in butadiene-palladium chloride and immersing the fabric in a nickel chloride bath with citric acid and dimethylamine borane.
German Published Application 2,820,502 published Nov. 15, 1979 in the name of Ebneth discloses electroless deposition of nickel on fabrics of PPD-T and poly(m-phenylene isophthalamide) (M-PDI) by pretreatment of the fabric with a colloidal solution of palladium in aqueous HCl.
European Patent Publication number 401,740, published Dec. 12, 1990 in the name of Lee, discloses fibers which include PPD-T and an additive amount of polyvinyl pyrrolidone (PVP) and a process for making such fibers. It is the fibers of that application which are used in practice of the present invention.
International Patent Publication WO 90/00634, published Jan. 25, 1990, discloses a process for plating a polymer wherein metal cations are electrostatically bonded to the polymer in a non-aqueous system and are, then, reduced to metal.